Source rocks, bitumens and petroleum inclusions from the Prague Basin (Barrandian, Czech Republic) - constraints for petroleum generation and migration from petrology, organic geochemistry and basin modelling

Volk, Herbert

Book	PreJuSER-62764

Volk, H. (Corresponding author)FZJ*

2000
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums Jülich 3825, XXI, 337 p. (2000)

Please use a persistent id in citations: http://hdl.handle.net/2128/20662

Report No.: Juel-3825

Abstract: The Prague Basin (Barrandian, Czech Republic) represents a classical locality for the Lower and Middle Paleozoic in Europe. Although so far no economic hydrocarbon accumulations have been detected, occurrences of biturnens and petroleum inclusions prove the generation and migration of hydrocarbons within the basin. Based on sedimentological and organic geochemical investigations a first systematic approach on the characterisation and classification of bitumens and petroleum inclusions has been carried out. Their relationship with possible source rocks, the thermal history of the basin and petroleum generation-migration has been analysed using field observations and microscopy, geochemical data and numerical simulations . Potential source rocks, ranging from Middle Ordovician to Middle Devonian, have been studied with respect to their source rock quality . Despite the advanced catagenetic stage of most of the screened strata, ranging from 0.75% (Srbsko Fm., Lower Givetian) to 2.34% (Letnd Fm., Middle Ordovician) reflectivity equivalent to vitrinite reflectance (VR, ~qw), total organic carbon (TOC) contents exceeding 1 % have been determined. The richest source rocks can be found in the Silurian where TOC values reach 2.62%. The hydrocarbon potential of Devonian strata is limited to the lowermost Lochkov Fm., directly succeeding the Upper Silurian . Rock Eval and open system pyrolysis data indicate the Silurian PoMry and Litefi Fm. to be the most prolific source rocks, with some residual hydrocarbon potential be recognised for the Middle to Upper Ordovician Letnd and Vinice Fm. Kerogen typing resulted in mixed type IUIII kerogens for all possible source rock horizons. Bitumens were found exclusively in Silurian and Devonian strata, hosted in veins, fossil molds or vuggy porosity. Black solid bitumen was present at all sampled localities, and in some outcrops greenish and orange, semi-liquid and waxy later stage bitumens occurred as well. Black solid bitumens are remnants of oils that have been thermally altered and influenced by weathering effects. Semi-liquid waxy biturnens are optically isotropic, show yellow fluorescence when excited with ultraviolet light and exhibit low reflectance values (<0.2%). They are interpreted as precipitates that have dropped out of ascending and cooling condensates. As these bitumens occur in hostrocks of an advanced catagenetic maturity stage and in fractures circulated by meteoric water, this mechanism must be a young phenomenon and is probably related to Tertiary block tectonics. Petroleum inclusions occur at all bitumen localities and can reach a remarkable size of up to 0.8 mm. Fluids are trapped in calcite and quartz crystals of diagenetic cements and vein mineralisations . In addition to pure aqueous and pure organic inclusions heterogeneous trappings

Note: Record converted from VDB: 12.11.2012

Contributing Institute(s):